This invention relates to sealed or bonded assemblies for lighting elements and to a novel method for producing same. In another aspect, sealed beam lamps and a method for producing same are described. In yet another aspect, an actinic light curable composition is utilized to seal a light transmissive lens cover to a concave, relfective housing to provide a lighting element.
For many years, the United States Department of Transportation has required the use of sealed beam headlamp assemblies on automobiles sold in the U.S. These assemblies generally comprise a substantially concave (preferably parabolic) lighting element housing and a visible light transmissive cover therefor, this cover often being referred to as a lens. The housing usually has a concave reflective surface and supports the lighting element so as to outwardly direct the light thereby generated through the lens.
The conventional technique employed to seal a cover (e.g. a lens) to a housing involves the application of heat to the respective peripheries thereof to fuse or weld the lens to the housing, the lighting element being interiorly disposed therein. This conventional technique has a tendency to develop internal strain in either the lens or the housing (occasionally resulting in breakage of the assembly). The problem of breakage has recently become of particular concern due to the now fashionable rectangular headlamps employed in the automobile industry. Breakage in the range of 10% to 20% has been reported for rectangular housing assemblies which are particularly susceptible to generation of unequal internal stress during the joining of the housing and its cover by the use of heat.
One possible solution to the aforementioned heat fusing breakage problem has been to utilize conventional heat-cured epoxy-containing materials to join the perimeters of the housing and the lens. While the temperature at which heat-cured epoxy resins may be cured is considerably lower than the temperature required to heat fuse the cover and lighting element housing, heating the assemblies long enough to bring about epoxy cure is costly.